Peptide Fragment and Residue-Range Notation
Residue-range notation names a peptide fragment by its parent and the positions it spans, as in GHRH(1-29) or PTH(1-34), with the numbers always referring to the parent's numbering rather than the fragment's.
A peptide fragment is a contiguous stretch cut from a longer parent, named by parent and span: PTH(1-34) is residues 1 through 34 of the 84-residue parathyroid hormone, GHRH(1-29) the first 29 of the 44-residue releasing hormone, hGH 176-191 the last sixteen of growth hormone's 191. The numbers always belong to the parent, as does the numbering of any substitution inside the fragment. Terminal groups ride outside the brackets: GHRH(1-29)-NH2 says the cut end has been amidated.
Teriparatide is PTH(1-34), approved in 2002 for osteoporosis; sermorelin is GHRH(1-29)-NH2, and tesamorelin, CJC-1295 and modified GRF(1-29) are built on the 1-44 or 1-29 frames. AOD-9604 is hGH 177-191 with a tyrosine in place of phenylalanine 176, and the shortened spadin analogue written 22-28 is numbered on the sortilin propeptide it was cut from.
The notation shows which part of a hormone a compound retains, and so which of the parent's evidence can transfer. A fragment that keeps the receptor-binding region and drops a regulatory tail can be a full agonist; one that keeps a tail without the binding region inherits nothing but a name. PTH(1-34) and PTH(1-84) both build bone; hGH 176-191 does not act at the growth hormone receptor at all.
The failures are numbering failures. A fragment renumbered from 1 and the same fragment in parent numbering look like two molecules. A range is also not a guarantee of sequence: hGH 176-191 is sold with the native phenylalanine and with AOD-9604's tyrosine at 176, and a GHRH(1-29) listing may or may not carry the four substitutions of modified GRF; bracketed substitutions and prefixes such as des-Gly10 carry that information, which the range never discloses.